Groundwater provides cool and clean water that keeps the rivers and streams flowing during the summertime. In New England, groundwater level is expected to respond more slowly to changes in precipitation than streamflow. This indicator is based on average depth to groundwater at USGS monitoring well ACW-158 in Acton over prior five summers (May through September). Although this is the only USGS monitoring well in the watershed, it is a good indicator of groundwater levels in the entire watershed’s glacial drift aquifers.